Developmental dysplasia of the hip (DDH) is a dislocation of the hip joint that is present at birth. The condition is found in babies or young children.

The hip is a ball and socket joint. The ball, called the femoral head, forms the top part of the thigh bone (femur) and the socket (acetabulum) forms in the pelvis.

The hip may be all the way out of the joint or the socket may be a little shallow. One or both hips may be involved.

The cause is unknown, but genetic factors may play a role. Low levels of amniotic fluid in the womb during pregnancy can increase a baby's risk of DDH. Other risk factors include:

• Being the first child
• Being female
• Breech delivery
• Family history of the disorder

DDH occurs in about 1 out of 1,000 births.

There may be no symptoms. Symptoms that may occur can include:

• Different (asymmetric) leg positions
• Reduced movement on the side of the body with the dislocation
• Shorter leg on the side with the dislocation
• Uneven folds of thigh fat

After 3 months of age, the affected leg may turn outward or be shorter than the other leg.

Pediatric health care providers routinely screen all newborns and infants for hip dysplasia. There are several methods to detect a dislocated hip or a hip that is able to be dislocated.

The most common method of identifying the condition is a physical exam of the hips, which involves applying pressure while moving the hips. The health care provider listens for any clicks, clunks, or pops.

Ultrasound of the hip is used to confirm the problem. An x-ray of the hip joint may help diagnose the condition in older infants and children.

A hip that is truly dislocated in an infant should be detected at birth, but some cases are mild and symptoms may not develop until after birth, which is why multiple exams are recommended. Some mild cases are silent and cannot be found during a physical exam.

In early infancy, a non-surgical positioning device is used to keep the legs apart and turned outward (frog-leg position). This device will usually hold the hip joint in place while the child grows. If there is a problem in maintaining proper position, a cast may be placed on the child's leg and changed as the child grows.

Surgery may be necessary if early measures to put the joint back in place are unsuccessful or if the problem is first detected in an older child.

If hip dysplasia is identified in the first few months of life, it can almost always be treated successfully with a positioning device (bracing). In a few cases, surgery is necessary to put the hip back in joint.

Hip dysplasia identified after early infancy may be associated with a worse outcome and may require more complex surgery to repair the problem.

Bracing devices may cause skin irritation. Differences in the lengths of the legs may persist despite appropriate treatment.

Untreated, hip dysplasia will lead to arthritis and deterioration of the hip, which can be severely debilitating.

Call your health care provider if you suspect that your child's hip is not properly positioned.

Stoker SK, Skaggs, DL. Developmental dysplasia of the hip. Am Fam Physician. 2006;74(8).

Mettler FA. Skeletal system. In: Mettler FA, ed. Essentials of Radiology. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2005: chap 8.